title: Innexins Ogre and Inx2 are required in glial cells for normal postembryonic development of the Drosophila central nervous system.
abstract: Innexins are one of two gene families that have evolved to permit neighbouring cells in multicellular systems to communicate directly. Innexins are found in prechordates and persist in small numbers in chordates as divergent sequences termed pannexins. Connexins are functionally analogous proteins exclusive to chordates. Members of these two families of proteins form intercellular channels, assemblies of which constitute gap junctions. Each intercellular channel is a composite of two hemichannels, one from each of two apposed cells. Hemichannels dock in the extracellular space to form a complete channel with a central aqueous pore that regulates the cell-cell exchange of ions and small signalling molecules. Hemichannels can also act independently by releasing paracrine signalling molecules. optic ganglion reduced (ogre) is a member of the Drosophila innexin family, originally identified as a gene essential for postembryonic neurogenesis. Here we demonstrate, by heterologous expression in paired Xenopus oocytes, that Ogre alone does not form homotypic gap-junction channels; however, co-expression of Ogre with Innexin2 (Inx2) induces formation of functional channels with properties distinct from Inx2 homotypic channels. In the Drosophila larval central nervous system, we find that Inx2 partially colocalises with Ogre in proliferative neuroepithelia and in glial cells. Downregulation of either ogre or inx2 selectively in glia, by targeted expression of RNA interference transgenes, leads to a significant reduction in the size of the larval nervous system and behavioural defects in surviving adults. We conclude that these innexins are crucially required in glial cells for normal postembryonic development of the central nervous system.
authors.affiliation: School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Holcroft
authors.forename: William D
authors.initials: WD
authors.lastname: Jackson
authors.forename: Wei-Hsiang
authors.initials: WH
authors.lastname: Lin
authors.forename: Kayleigh
authors.initials: K
authors.lastname: Bassiri
authors.forename: Richard A
authors.initials: RA
authors.lastname: Baines
authors.forename: Pauline
authors.initials: P
authors.lastname: Phelan
mesh_terms: D000818:Animals; D001483:Base Sequence; D002490:Central Nervous System / Q000196:embryology* / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D014982:Xenopus laevis / Q000196:embryology
chemical_list: D017630:Connexins; D029721:Drosophila Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; C120024:inx2 protein, Drosophila; C079326:ogre protein, Drosophila
keywords: Connexin; Drosophila; Gap junction; Glia; Innexin; Nervous system